package pta.期末训练集.合法标识符06;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()){
            String s = sc.nextLine();
            int flag=0;
            for (int i = 0; i < s.length(); i++) {
                char c = s.charAt(i);
                if (i==0){
                    if (Character.isJavaIdentifierStart(c)){
                        flag=1;
                    }else {
                        flag=0;
                        break;
                    }
                }else {
                    if (Character.isJavaIdentifierPart(c)){
                        flag=1;
                    }else{
                        flag=0;
                        break;
                    }
                }
            }
            if (flag == 1) {
                System.out.println("true");
            }else {
                System.out.println("false");
            }
        }
    }
}
